1. Field of the Invention
The present invention relates to an adhesive composition and a sheet for forming a semiconductor wafer-protective film for forming a film to protect the back surface of a semiconductor wafer when dicing the semiconductor wafer.
2. Description of the Related Art
A flip-chip bonding method has been used so as to make a mounting area of a semiconductor chip small. Usually in this connection method, the following procedure is employed: (1) forming circuits and bonding bumps on the front surface of a semiconductor wafer, (2) polishing the back surface of the semiconductor wafer to a prescribed thickness, (3) dicing the semiconductor wafer to obtain a semiconductor chip, (4) connecting the chip to a substrate with arranging the circuit-formed surface of the chip to face the substrate and then (5) performing resin-molding or the like to protect the semiconductor chip.
However, fine streaky scratches are occasionally formed on the back surface of the semiconductor wafer in the polishing process (2) to cause crack generation after the dicing process and the packaging process. Accordingly, it has been proposed to form a protective film (a protective film for chips) on the back surface after the polishing process (2) so as not to adversely affect the subsequent processes even in the case that such damages are formed in the polishing process. Furthermore, a sheet for forming such a protective film, which is composed of a release sheet and a protective film-forming layer formed on the release-side surface of the release sheet, has been proposed (Japanese Patent Laid-Open (kokai) No. 2002-280329 and Japanese Patent Laid-Open (kokai) No. 2004-260190).
Meanwhile, in the dicing process, it has been known that a wafer is occasionally damaged due to vibration of a rotary blade (dicing blade) or the like (hereinafter referred to as “chipping”).
It is also expected that the protective film for chips prevents chipping in the dicing process. However, when the protective film is not even, a gap is caused between a dicing film and the protective film, that is, a region where the dicing film does not contact the protective film is caused. Due to this unevenness of the protective film, there has been a problem that the nonuniform air layer between the protective film and the dicing film makes the rotary blade vibrate during cutting the wafer to further damage the wafer.